WASHINGTON - At least one US national was killed and another injured following Wednesday's "highly unusual" shooting by Cuba's border guards at a US-registered speedboat, multiple US media outlets reported Thursday, citing US officials.

The injured US national is now receiving care in Cuba. The speedboat's owner reported that the 24-foot vessel had been stolen by an employee in Florida, US officials told Axios, a US news website. Four people were killed and six injured in the shooting.

US Secretary of State Marco Rubio has officially asked Cuba for access to the six injured people, a US official told Axios.

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Some of those aboard the boat sailing from the Florida state have criminal records, according to the Axios report.

At least one person aboard has a current US K-1 visa, a non-immigrant visa allowing a foreigner to enter the United States (US) to get married to a US citizen, said the report.

Others who were aboard the boat are believed to be legal permanent residents of the United States, the report added.

Rubio said on Wednesday that the administration of US President Donald Trump is probing the deadly shooting, and confirmed the shooting did not involve US government personnel or operations.

"As we gather more information, we'll be prepared to respond accordingly," said Rubio.

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The shooting came amid rising tensions between the United States and Cuba as the island country in the Caribbean is facing rapidly worsening conditions driven by severe fuel shortages, prolonged blackouts and growing barriers to accessing food and healthcare.